Method of making a bonded poriferous non-woven textile fabric



l. s. Nass 3,485,695

METHOD OF MAKING A BONDED PORIFEROUS NON-WOVEN TEXTILE FABRIC Dec. 23,1969 2 Sheets-Sheet l Original Filed July 31, 1964 .mmf

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Dec. 23, 1969 l. s. Ness 3,485,695

METHOD OF MAKING A BONDED PORIFEROUS NON-WOVEN TEXTILE FABRIC OriginalFiled July 3l,LA 1964 2 Sheets-Sheet 2 ZM/,Mba T- ma# ATTORNEY UnitedStates Patent O 3,485,695 METHUD OlF MAKING A BONDED PORTFEROUSNON-WOVEN TEXTILE FABRIC llrving S. Ness, Princeton, NJ., assignor toJohnson & Johnson, a corporation of New Jersey Continuation of abandonedapplication Ser. No. 386,713, July 31, 1964. This application Jan. 26,1968, Ser. No.

rut. ci. non; 1/64 U.S. Cl. 156-229 2 Claims ABSTRACT OF THE DISCLOSUREA method of making a bonded, poriferous non-woven textile fabric isdisclosed, said fabric having no significant extensibility in the longdirection and having undirectional cross elasticity.

This is a continuation of application Ser. No. 386,713, filed July 31,1964 now abandoned.

This invention relates to nonwoven fabrics, i.e., fabrics produced fromtextile fibers without the use of conventional weaving and knittingoperations, and more particularly to nonwoven fabrics havingunidirectional elasticity.

Nonwoven fabrics of various types have become increasingly important inthe textile field during the past decade, primarily because of their lowcost of manufacture compared to fabrics formed by weaving or knittingspun fibers. Nonwoven fabrics are particularly suitable for applicationswhere launderability is not a prerequisite, or low cost is an importantconsideration, especially in the case of finished products that are usedonce and then discarded as, for example, in the manufacture of sanitarynapkins, surgical dressings, hospital caps, casket liners, disposabletable napkins, hand towels, diapers, drapery fabrics, disposablegarments and the like.

The' instant invention provides a poriferous nonwoven fabric of bondedtextile fibers, said fabric having unidirectional elasticity.

A nonwoven textile fabric is usually thought of as having twodirections, i.e., the machine direction and the cross direction; themachine direction being the direction that the web of textile fiberstravel, i.e., from machine station to machine station, as it ismanufactured. It is defined by being parallel to the longitudinal axisof the fabric during manufacture. The cross direction is at right anglesto the machine direction and defines the width of the fabric or itslateral axis.

More particularly the instant invention provides a poriferous nonwoventextile fabric of bonded textile fibers, the perimeter of each of saidpores being defined by bundles of rearranged textile fibers, said poresbeing arranged columnwise in staggered relationship to correspondingpores defining immediately adjacent columns, said fabric havingunidirectional elasticity.

The fabric of this invention is said to have unidirectional elasticitysince it possesses elasticity, i.e. elongation and rapid recovery, ineither the machine or the cross direction, depending on its method ofmanufacture; however, this is its major component of elasticity since itis understood that it will have elasticity in the bias.

The fabric of the invention is produced by a process comprising (l)forming a laminate of a plurality of tenuous webs of loosely associatedtextile fibers dispersed in sheet form, (2) subjecting said laminate tofiber rearrangement to provide systematically staggered porestherethrough, (3) bonding said poriferous or foraminous fabric toprovide integrity, (4) drying fabric, (5) drafting said fabric to causeunidirectional extension, (6) ap- "ice plying an elastomeric binder tosaid extended fabric, and (7) drying said fabric while it is held insaid extended position.

The textile fibers used in the production of this fabric may be eitherindividualized fibers, tow, monofilaments or continuous filaments;however, individualized fibers are preferred and these vary fromapproximately 1/2" to 2" in length. The fibers may be either natural ormanmade, i.e. polymers synthesized by man, modied or transformed naturalpolymers and glasses. They may be elastomeric, in and of themselves,thereby contributing to the elasticity of the final fabric; however, theinitial elasticity produced in the fabric by re'ason of this inventionis not in any manner dependent upon the fibers possessing inherentelasticity.

Webs of textile fibers are formed by processing the fibers through anysuitable machinery to form a sheet of loosely associated fibers. In thisweb-forming process it is preferred that the fibers be first carde'd;however, this is only a preference and no unsatisfactory results appearif this step is deleted.

The webs or sheets of fibers are preferably superimposed to provide alaminate of from about 300 grains per square yard to about 1200 grainsper square yard. Below about 300 grains per square yard the laminate istoo weak or lacks suicient strength to undergo the necessary additionalprocessing. The upper limit is only a practical maximum since it isdictated by the necessity to next bond the laminate to provide integrityand since beyond this limitation, bonding becomes difficult usingexisting methods and techniques. If the webs or sheets are random lay,i.e., by the air laying of fibrous webs, as for example, by theRando-Web process, lamination is not necessary since the web hassufiicient substance. The preparation of a laminate, however, is themost preferred embodiment and insures the most desirable results.

Having provided the laminate, it is processed to rearrange theindividual fibers which define it and thus to provide a poriferousstructure whereby the perimeter of each of the pores is defined bybundles of these rearranged textile fibers and whereby the pores aresystematically arranged columnwise' in staggered relationship tocorresponding pores defining immediately adjacent columns. This could beaccomplished by any feasible method but is preferably accomplished bythe method and apparatus disclosed in U.S. 2,862,251.

The laminate is then bonded With adhesive or cementitious materials toprovide sufiicient integrity to allow it to be processed further withoutbreaking up. The bondin g operation employed for stabilizing andstrengthening nonwoven fabrics has taken on many forms, one popular formbeing the intermittent bonding of the nonwoven fabric with apredetermined pattern of spaced discrete binder areas or lines extendingacross the width of the nonwoven fabric. The individual fibers passingthrough these binder areas or lines are adhered into a stableselfsustaining relationship. The binder areas may also take on anydesire'd shape or form including circles, annuli, ovals, elipses,triangles, rectangles, squares, diamonds, parallelograms or otherpolygons or combinations of such forms either regular or irregularshaped. The binder lines may extend across the nonwoven fabric at anydesired angle to the long axis; the binder lines may be parallel, orthey may cross each other to form diamond or irregular polygonicfigures; the binder lines may be continuous or discontinuous; or theymay be straight, curved, sinuous 0r irregularly wavy.

One common factor, however, is to be particularly noted in all of thesepatterns; namely, that the total surface coverage of the binder areas orlines of the nonwoven fabric should not substantially exceed about 35%of the total surface of the nonwoven fabric. Preferably such coverageshould be less than about 25% and sometimes down to about 8% of thetotal surface of the nonwoven fabric. The minimum amount of binder canbe determined by the minimum amount of binder add-on which is solidsadd-on.

The binder may also be applied by impregnation, as for example, bypassing the fabric through a padder bath and this represents thepreferred procedure and results in the most satisfactory product. It isimportant, in this event, that about at least 5% solids is distributeduniformly throughout the thickness of the fabric. Of course, the bindermay be applied using any of the common techniques known to the art.Preferably, if you print bond there should be from about 10 to about 15%binder addon and if you impregnate you would preferably have about 10%binder solids add-on.

The fabric is then dried to develop the bond.

The binder material which is to be used to provide integrity to thelaminate or to the poriferous structure is generally defined as any ofthe common binders available to the textile art provided it has a fairdegree of Wet strength; however, if the impregnation technique isutilized the binder used must have a measurable amount of elasticity.Representative examples of some of these binding materials are polyvinylacetate, polyvinyl chloride, yacrylate, natural or synthetic rubber, andthe like. Viscose can be utilized only if the impregnation technique isnot employed since it has no elastic properties.

Having bonded the poriferous structure it is now dried to effect thebond. The dried fabric is then drafted, drawn or extended, preferably inthe machine direction; this is accomplished by drawing the fabricbetween two nips or control points running at different speeds. Thefabric may be drawn up to any point short of fabric destruction or aslittle as desired depending upon the amount of elongation and rapidrecovery that is desired in the finished fabric.

Retaining the fabric under tension, it is now bonded with an elastomericbinding material and heat is applied to the binder. Throughout theoperation, i.e., the application of binder and the drying, the fabric iskept under tension to allow the binder to set and cure and thus retainthe fabric in this extended condition. The resultant fabric now hasunidirectional elasticity.

The elastomeric binder is generally defined as any binder exhibitingelastomeric properties or any binder that has been termed rubber by theart. Preferably the elastomeric binder is any polymer that has elasticproperties and is cross-linked by covalent bonds and will recover, afterelongation, with a good power factor. Most preferably a cross-linkedacrylic binder is desired since it is defined by chemical stability,resistance to oxidation and to discoloration.

As an alternative to the above-described procedure, the fabric Imay bebonded after fiber rearrangement followed by a combination of draftingto the desired elongation or extension and drying to set the binder andto insure the extended fabric position in the absence of forcedextension in the direction of draft. The greatest proportion ofextension is given to the fabric if it has been wetted. This wetting canbe accomplished by the application of binder or by the utilization of aseparate wetting step.

Additionally, a greater degree of elasticity may be supplied if thefiber of the fabric is cotton or rayon or a combination thereof. Thiswould be accomplished by incorporating a cellulose-reactive constituentinto the elastomeric binder composition which will provide, after cure,a cross-linking of the cellulosic fibers and an increase in the modulusof the fabric over that fabric elasticity which would have existed inthe absence of the cellulose-reactive constituent.

The fabric of this invention is a nonwoven which is preferablyconstructed of individualized textile fibers. It has been rearranged toprovide pores which are positioned in columns, but in staggeredrelationship to corresponding pores defining immediately adjacentcolumns. The fabric has, during manufacture, been extended in onedirection, i.e., the machine or cross direction, and bonded in position;therefore, the pores have a longitudinal axis extending in the directionthat the fabric was extended or drafted and a shorter lateral axisextending at subtsantially right angles to the former. Regardless of theoriginal configuration of the pores prior to the drafting operation theyare elongated in the final product and each possesses one longitudinalaxis extending in the same direction as the direction in which thefabric has been extended during manufacture. For the sake of simplicitythis direction of extension shall hereinafter be termed the draftdirection of the fabric or the draft direction.

The present invention will be more fully understood with reference tothe following detailed description and the accompanying drawings inwhich:

FIGURE l is a schematic illustration of the process for forming thefabric of this invention;

FIGS. 2 and 3 are enlarged idealized representations of an intermediatefabric of the invention;

FIG. 4 is an enlarged idealized representation of one embodiment of thefabric of this invention; and,

FIG. 5 is a diagrammatic representation of the properties exhibited bythe fabric of this invention.

More specifically, FIGURE l recites the steps of the process forproducing the elastic nonwoven fabric. As is indicated, the webs oftextile fibers are first formed and then superimposed to produce alaminate. The laminate is caused to undergo fiber rearrangement toeffect the poriferous fabric and then bonded and dried to providesufficient integrity to permit the fabric to undergo the furtherprocessing. This is followed by unidirectional drafting and bonding withan elastomeric binder while the fabric is in extended position. Thefabric is then dried in this extended state.

FIGS. 2 and 3 represent embodiments of intermediate fabrics of thisinvention taken after the fiber rearrangement step of the process butprior to the drafting step. With specific reference to FIG. 2, themachine direction is given by the arrow and the letter M while the crossdirection of the fabric runs at right angles to the direction M.

The fabric 1 is poriferous as is evidenced by the pores 2 and isconstructed of individual fibers 3 which have been rearranged intobundles defining the perimeters of the pores 2. The pores 2 are shown asextending into columns A, B and C, respectively, which run in themachine direction and in rows E, F, G and H which run in the crossdirection. It is essential that the pores of any one column be instaggered relationship to the pores of the immediately adjacent columnsas, for example, the pores of column B are staggered with respect to thepores of columns A and C, i.e., the pores of A and C do not occupy aposition in rows F and H as do the pores of column B but rather in rowsE and G.

The imaginary trapezoid 4 is taken along the'centers of the two pores 2in columns B and from the center of each of the respective poresn 2 incolumns A and C. It is to be noted that the acute angles X of thetrapezoid are both positioned along row G and in columns A and C, Whilethe obtuse angles Y are both positioned along column B in rows F and H.The pores 2 are substantially circular and the fabric has been bondedsufficiently to provide the necessary integrity to the poriferouslaminate to permit it to undergo the further processing required Withoutbreaking up.

The fabric of FIG. 3 differs from that of FIG. l only insofar as thepores are hexagonal rather than circular and insofar as the fibers ofthe initial webs were randomly positioned in the fabric of FIG. 2whereas they were carded and thus oriented in the webs comprising thefabric of FIG. 2. Particular attention is invited to the fact that inFIG. 3 there are two parallel sides 5 and 6 of each pore running in themachine direction for a measurable distance.

FIG. 4 is meant to represent the same section of the fabric shown inFIG. 2 with the sole exception that the fabric depicted is now thefinished fabric as opposed to the intermediate fabric of FIG. 2.

The fabric of FIG. 4 has undergone all the processing steps describedearlier (see FIG. l) and has therefore been drafted. Unidirectionaldrafting of the fabric has been accomplished in the machine direction Mas is evidenced by the elongated condition of the pores 2. The pores 2are each now characterized as having a long longitudinal axis 7extending in the direction in which the fabric has been drafted and ashort lateral axis 8 at substantially right angles to the former. Theangles X of the trapezoid 4 which were the acute angles in FIG. 2 arenow the obtuse angles and angles Y have become the acute angles. Thus aparallel-motion mechanism, or parallelogram-type device familiar as lazytongs, collapsible gates, or the pantograph device utilized in draftinghas been eected and is represented by the imaginary trapezoid of bothFIGS. 2 and 4.

In FIG. 4 since this represents one embodiment of the linished fabric ofthis invention, it has been drafted in the machine direction and bondedin position with an elastomeric bonding material. It has then beenprocessed so that its permanent position is represented by that depictedin FIG. 4. Attempts at fourth extension in the direction of drafting ofa fabric will be of no avail and in fact the fabric will exhibitexceptional strength in the direction M; however, extension in the crossdirection C in this instance, i.e., in the direction at right angles tothe direction of drafting, will be evidenced by elasticity orspecifically by fabric extensibility in that direction and fabricrecovery to substantially the position shown in FIG. 4. The fabric ofFIG. 4 can be extended in direction C to a point just before the ruptureof the fabric, i.e to a point just before bers are broken and/or fabricbond sites are ruptured. The degree of recovery is exceptional.

In FIG. 5 the percent recovery of the fabric of this invention isplotted against the specific elongation which the fabric is made toundergo and the results are plotted.

The fabric is that made via Example l and the results show the excellentelongation and companion recovery exhibited by the fabric.

Referring, after the above explanation, to the fabric depicited in FIG.3, it is now pointed out that any side to the pores such as sides S and6 which have measurable distance in one parallel or substantiallyparallel direction will act to diminish the degree of elasticity whichthe fabric exhibits since they become rigid members of the pores 2 whichhamper or lessen the functioning of the lazy tong principle of theinvention.

Each of the pores of the fabric must have a diameter within the range offrom about 0.020 to about 1A taken across its longest axis, since belowabout 0.020 the amount of extensibility exhibited by the fabric isnegligible and the pores or holes are of insufficient dimensions toeffect the desired lazy tong result and since above about 1A" indiameter the requisite bundles of textile fibers cannot be formed duringthe fiber rearrangement or in other words the desired pores cannot beproduced.

The sum total of the open area per square inch of the fabric must bewithin the range of from about to about 50% open area or in terms of thenumber of pores per square inch, from 400 to 10 per square inch. Belowthe minimum open area the amount of extensibility or elasticityexhibited by the invention is negligible and with an open area above 50%, the pore formation is poor and the fabric loses its integrity.

The pores may be of any configuration although as mentioned earlierstraight line sides of a pore as for example in any polygonconfiguration, Where these straight line sides extend at substantiallyright angles to the direction of the unidirectional elasticity of thefabric and where the straight sides do have some measurable dimensionwill hamper the invention and will act to lessen the elasticity. Thepores should also be ofthe same or very similar configuration and ofapproximately the same size to avoid discontinuities in the fabric andto contribute to the maximum functional efliciency of the elasticnonwoven fabric.

The pores are positioned systematically in columns in the fabric and inrows extending at right angles to the columns and in staggeredrelationship thereto. They are positioned systematically in columns toprovide a regular reoccuring sequence =which will contribute to theuniform unidirectional elasticity throughout the fabric. Randomizedpositioning would severely lessen the elasticity. The individual poresof any one column must be arranged in staggered relationship to thecorresponding pores defining immediately adjacent columns in order toallow the perfection of the lazy tong principle on which theunidirectional elasticity of the fabric depends. Thus the line drawnthrough the centers of the pores of any one row will not bisect thecenter of any pore or pores defining two adjacent columns of pores. Ascan be realized, a pattern effect can be imparted to the fabric by thepores and still not impair the fabric elasticity, as long as the samepattern of pores reoccurs throughout the fabric systematically inregular occuring sequence and so long as the pores comprising eachindividual pattern are arranged in the same column row-staggeredrelationship defined above.

In providing the required relationship between the pores of the columnand those of the rows such that the pores arranged columnwise are instaggered relationship to the corresponding pores defining immediatelyadjacent column, it is only necessary to insure that the centers of anythree pores, each in an immediately adjacent column, do not coincidesuch that they, i.e., the three pores, lie in `a single row running atright angles to the columns. Of course, the ideal arrangement to providemaximum unidirectional elasticity in the fabric would be to position thepores of any one row with respect to the pores of any one column suchthat lines drawn from the centers of two successive pores in one columnto the center of an adjacent pore interposed in a row between them, willproduce an angle approaching 0 at their juncture at the center of thepore in the row.

The unidirectional elasticity of the fabric lis provided by theutilization of the lazy tong principle which is realized by theessential pore and hole positioning and configuration in the fabric andby the drafting or extending of the rearranged fabric in one directionfollowed by the bonding with an elastomeric binder while the fabric isheld in an extended position so that the hinder is permitted to setwhile the fabric is in that extended state. Since the fabric has thenbeen extended and bonded s0 that this extension is retained, the fabricdoes then exhibit excellent strength but no significant elongation inthe draft direction. It does, however, exhibit excellent extensibilityand recoverability in the direction substantially at right angles to thedraft direction of the fabric. The percent elongation that the fabricwill possess will range from about 15% to about 200% and it will beuniform. The elongation may be termed cross extensibility since it is ina direction substantially at right angles to the draft direction of thefabric. The fabric, having been extended to just below its ruptureelongation, i.e., to of break, will have at least a 50% recovery whichis, in most instances, followed by an elastic aftereffect (following theinitial rapid retraction of the extended article) which will slowlycause the total recovery to approach The invention will be more fullydescribed in the following example Which is illustrative and in whichparts and percentages are by weight unless otherwise specified.

EXAMPLE l A fabric is made by laminating oriented card webs to a Weightof 330 grains per square yard. The fiber comprises 75% extra dull and25% regular dull viscose rayon Pounds Karamul 142 ST 200 Water 200Catalyst A 1 The pH of the binder is adjusted to approximately 7 withammonia. The padded web is dried over steam cans operating at 275 F. Thebinder picked up is such as to add 35 grains per square yard of drybinder solids so that the total finished weight is 365 grains per squareyard.

This base fabric is further processed by passing through another paddercontaining a solids bath of Karamul 142 (manufactured by RefinedProducts Company and formulated as above except to 5% solids level). Thewet out fabric is dried over steam cans operating at 275 P. The steamcans are operated at a faster line speed than the padder so as to effecta drafting of the wet web between the two units. The resin applied,which is soft and elastomeric, is caused to be set while the fabric isstretched and locks the lazy tongs in a closed position. The driedfabric has substantial widthwise extensibility as the tongs open. Thisfabric has a resultant cross-extensibility of 170% and substantially100% recoverability. In this instance, the fabric fed to the padder is44 inches Wide. Due to the drafting, it is reduced to 28 inches in widthat the dry cans. It is to be appreciated that the drafting also affectsthe fabric weight per unit area. In this instance, the final stretchfabric weighs 750 grains per square yard. This comprises approximately450 grains per square yard of fiber and 300 grains per square yard oftotal binder solids.

The fabric can be treated although the softness and hand of the finishedarticle are satisfactory.

The fabric can be treated to be made Waterproof and can be treated toprovide additional softness, hand, etc., although the softness and handof the finished article are satisfactory. It rcan also be dyed orotherwise colored and can, in general, be treated in accordance withthose methods and ultimate desires presently practiced with nonwovenfabrics.

What is claimed is:

1. The process for producing a poriferous non-woven fabric having nosignificant extensibility in the long direction and havingunidirectional cross elasticity defined by an elongation in the range offrom about to about 200% and an elastic recovery after elongation to 80%of break of at least 50% rapidly and approaching 100% slowly whichcomprises:

(1) forming a laminate of a plurality of tenuous webs of looselyassociated textile fibers dispersed in sheet for-m;

(2) subjecting said laminate to ber rearrangement to provide aporiferous fabric having systematically staggered pores therethrough;

(3) bonding said poriferous fabric to provide integrity;

(4) drying;

(5) drafting said fabric in the long direction thereof in an amountshort of fabric destruction to cause unidirectional long extension andunidirectional crosswise reduction whereby said pores become elongatedand have a long longitudinal axis and a short lateral axis;

(6) applying an elastomer binder to said extended fabric; and

(7) drying said fabric while it is held in said extended position toprovide pores having a diameter within the range of from about 0.02" toabout 1A" taken across the long axis of said pores, and said fabrichaving an over-all open area of at least about 20%, whereby said fabrichas no significant extensibility in the long direction but has excellentextensibility and recoverability after extension in the cross direction.

2. The process for producing a poriferous non-woven fabric having nosignificant extensibility in the long direction and havingunidirectional cross elasticity defined by an elongation in the range offrom about 15 to about 200% and an elastic recovery after elongation toof break of at least 50% rapidly and approaching 100% slowly whichcomprises:

(1) forming a tenuous web of loosely assoicated textile fibers dispersedin sheet form;

(2) subjecting said web to fiber rearrangement to provide a poriferousfabric having systematically staggered pores therethrough;

(3) bonding said poriferous fabric to provide integrity;

(4) drying;

(5) drafting said fabric in the long direction thereof up to about 80%of break to cause unidirectional long extension and unidirectionalcrosswise reduction whereby said pores become elongated and have a longlongtiudinal axis and a short lateral axis;

(6 applying an elastomer binder to said extended fabrics; and

(7) drying said fabric while it is held in said extended position toprovide pores having a diameter within the range of from about 0.02 toabout 1A taken along the long axis of said pores, and said fabric havingan over-all open area of at least about 20%, whereby said fabric has nosignificant extensibility in the long direction but has excellentextensibility and recoverability after extension in the cross direction.

References Cited UNITED STATES PATENTS 2,697,678 12/1954 Ness et al161-170 X 2,862,251 12/1958 Kalwaites 161-169 X 2,958,608 11/1960Barnard 161-138 X 3,081,515 3/1963 `Griswold et al. 161-169 X ROBERT F.BURNETT, Primary Examiner LINDA M. CARLIN, Assistant Examiner Us. C1.XR.

